NX1279 Improvements
Posted: Mon Feb 04, 2013 9:18 pm
So I've enjoyed some nice cross country trips in NX1279, but they weren't exactly fast trips. 85mph was about all I was getting which seemed a little slow for a O-290 powered ship. After last summer's flying adventures, I decided to see what I could do to clean the airplane up to squeeze a little more speed out of it. The first thing I did was replace the Aeromatic prop with a Culver fixed pitch wood prop. I didn't notice any big speed increases, maybe 5mph but I was getting that same speed at about 200 rpm less and the climb performance didn't seem to suffer at all. I think Aeromatics are great props, but not well suited to slow draggy airplanes like the Hatz.
Next I installed wing gap fairings for the lower wings. While these aren't shown on the plans, I think most builders install them. They were one of those things I always meant to get to, but you know how it is. Once you get the airplane flying, it's too much fun and you mentally switch from the building mode to the flying mode. Anyway, I couldn't believe what a difference those gap seals made. An honest 10 mph increase. I was shocked. It also made the stall even slower and more gentle.
I added some gap seals on the elevator. No noticeable speed increase, but made the elevator feel a little lighter.
Next on the list was windshields. The rear cockpit has always been really windy. I was just about to start making a new larger rear windshield and frame, but had the idea to removed the front windshield first to see what kind of difference that made. It was night and day. Much calmer in the rear, although noticeable more windy on my feet now. I decided I could live with the rear windshield now, especially because I know how much time it takes to make that frame.
I now needed something to keep the wind off my feet. I'd made a canvas rain cover for the cockpits, so I snapped the front cover on and fired it up to see how it reacted. I was most worried about the cover trying to lift, but as soon as I ran the engine up, is was clear that the force on the cover was straight down. Really high pressure in that area, which is what I was feeling on my feet. I actually tried one flight with the canvas cover, but it was a little unnerving to see how much it was deflected down, so I decided to make a hard cover.
I had some .050 6061 laying around, so I made a pattern and formed it to conform to the cockpit coaming. It's held in the front and on the sides with some Z brackets that hold the cover in place. In the rear I just picked up one of the 8-32 holes that hold the cockpit sheet metal in place.
Took the new cover for a ride this evening and it was solid as a rock.
At this point I'm indicating 105 mph at 2400 rpm, which is a big improvement considering I only hold 18 gallons. I figured that most cross country trips are solo so there's no loss in covering the front pit. When I take the plane to the midwest this summer, I'll do the cross country with the cover in place and the windshield removed. Once I get there, the process is easily reversed for giving rides.
Got some wheel pants I'm making out of aluminum, but they're kind of on the back burner due to some of the other projects in the shop right now.
Anyway, that's what I've been up to. It would be interesting to find out what kind of performance others are getting with the various engine/prop combos.
Mark
Next I installed wing gap fairings for the lower wings. While these aren't shown on the plans, I think most builders install them. They were one of those things I always meant to get to, but you know how it is. Once you get the airplane flying, it's too much fun and you mentally switch from the building mode to the flying mode. Anyway, I couldn't believe what a difference those gap seals made. An honest 10 mph increase. I was shocked. It also made the stall even slower and more gentle.
I added some gap seals on the elevator. No noticeable speed increase, but made the elevator feel a little lighter.
Next on the list was windshields. The rear cockpit has always been really windy. I was just about to start making a new larger rear windshield and frame, but had the idea to removed the front windshield first to see what kind of difference that made. It was night and day. Much calmer in the rear, although noticeable more windy on my feet now. I decided I could live with the rear windshield now, especially because I know how much time it takes to make that frame.
I now needed something to keep the wind off my feet. I'd made a canvas rain cover for the cockpits, so I snapped the front cover on and fired it up to see how it reacted. I was most worried about the cover trying to lift, but as soon as I ran the engine up, is was clear that the force on the cover was straight down. Really high pressure in that area, which is what I was feeling on my feet. I actually tried one flight with the canvas cover, but it was a little unnerving to see how much it was deflected down, so I decided to make a hard cover.
I had some .050 6061 laying around, so I made a pattern and formed it to conform to the cockpit coaming. It's held in the front and on the sides with some Z brackets that hold the cover in place. In the rear I just picked up one of the 8-32 holes that hold the cockpit sheet metal in place.
Took the new cover for a ride this evening and it was solid as a rock.
At this point I'm indicating 105 mph at 2400 rpm, which is a big improvement considering I only hold 18 gallons. I figured that most cross country trips are solo so there's no loss in covering the front pit. When I take the plane to the midwest this summer, I'll do the cross country with the cover in place and the windshield removed. Once I get there, the process is easily reversed for giving rides.
Got some wheel pants I'm making out of aluminum, but they're kind of on the back burner due to some of the other projects in the shop right now.
Anyway, that's what I've been up to. It would be interesting to find out what kind of performance others are getting with the various engine/prop combos.
Mark